1. Technical Field
The present invention relates to a technology for an image forming apparatus and more particularly to a technology for transporting a carriage on which a print head is mounted.
2. Related Art
In general, an ink jet printer is provided with a carriage on which a print head is mounted for discharging ink, and a carriage drive mechanism that slidably supports the carriage by means of a guide shaft and allows the carriage to reciprocate along the guide shaft. The carriage may vibrate (swing) due to the moment of force that is applied when the carriage accelerates or decelerates during its reciprocating movement. The swinging of the carriage causes poor printing quality.
JP-A-2003-158614 describes a technology that reduces a possibility that the swinging of a carriage can occur. JP-A-2003-158614 discloses an image reader having an image sensor that reads a document put on a flatbed, a carriage on which the image sensor is mounted, and a guide shaft for allowing the carriage to move. The carriage is provided with a stationary slide member and a pressing slide member, which engage the guide shaft. The stationary slide member is in contact with the guide shaft and thereby positioned in a direction perpendicular to a direction in which the stationary slide member moves. The stationary slide member and the pressing slide member, which is pressed by a pressing spring from a side opposite to the stationary slide member, clamp the guide shaft. In this manner, when a load is applied due to the movement of the carriage, swinging of the carriage is prevented by the urging force that results from the contact of the stationary slide member with the guide shaft and the pressing force applied to the guide shaft by the pressing slide member.
In recent years, printers have tended to be provided with an increased number of ink cartridges so as to produce high-quality printed images. As a result, the weight and size of a carriage on which the ink cartridges are mounted have also increased. In this trend of increasing number of ink cartridges, in order to suppress an increase in size of a printer, a printer of a type having ink cartridges that are separate from a carriage has been developed. The printer of a type having ink cartridges that are separate from the carriage has a structure in which the ink cartridges are arranged in a dead space within the body of the printer, and ink is supplied from the ink cartridges through a flow passage, such as a tube, to a print head that is mounted on the carriage.
The printer of a type having ink cartridges that are separate from the carriage, however, has a problem as described below. Specifically, the carriage will receive the moment of force due to elastic force of the tube, in addition to the moment of force due to inertial force and frictional force, which are applied to the carriage when the carriage accelerates or decelerates during its reciprocating movement. The magnitude and direction of the moment of force that the carriage receives due to the elastic force depend on a position of the reciprocating carriage. The magnitude of the moment of force due to the elastic force may be several times larger than that of the moment of inertial force that counters the moment of force. Therefore, there is a high possibility that swinging of the carriage can occur in a printer of this type.
JP-A-2003-158614 describes a technology that is directed toward preventing swinging due to the moment of force that the carriage receives during its reciprocating movement, and that does not assume that the moment of force received is several times larger than the moment of inertial force acting against that moment of force. If the technology described in JP-A-2003-158614 is applied to the printer of a type having ink cartridges that are separate from the carriage, it requires employing a large pressing spring, thus making the size of the apparatus large.